From: emory!mcigate.apdev.cs.mci.com!rmwise (Bob_Wise)
X-Source: The Hotrod Mailing list
Date: Apr 1993
Subject: Re: long rod 351W
X-Sequence: 5102
On Apr 22, 1:34, The Hotrod List wrote:
> Subject: Re: long rod 351W
> Results are always conclusive when they're repeatable. Again, the kind
> of engines Circle Track is usually talking about are what's in your race
> car, not what's in your car hauler, which is what the long-rod 351 was
> supposed to be.
Were they not repeatable?
> rod is nearly straight up and down, and even tremendous amounts of extra
> pressure won't help the dyno figures much. High *peak* pressure is
Sounds like a good application for another idea Smokey's been pushing
then, offset wrist pins.
-Bob
[Offset pins work well and have been pretty standard in racing motorcyle
engines for over 30 years. The problem with them is there is a strong
rocking couple at BDC that causes strong slapping. If there is just
a bit of excess skirt clearance, the slap will break the skirt. voice
of experience talking. Not much of a problem with high-buck racing
engines that get new pistons fairly often but a REAL problem with
econo-motors operated by people with zero budget (me!) I started mounting
the piston reversed (a la street engines) in order to be able to run
a season on a piston. A little less power but no more broken skirts.
JGD]
--
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| Bob Wise | INET:622-1322 | MCIMail:468-2222 | Pager:719-577-1928 |
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From: emory!VAX1.Mankato.MSUS.EDU!KOOLGUY
X-Source: The Hotrod Mailing list
Date: Apr 1993
Subject: Re: long rod 351W (question)
X-Sequence: 5127
X-News: mkvax1 alt.hotrod:1610
>From: hotrod@dixie.com (The Hotrod List)
>Subject:Re: long rod 351W
>Date: Thu, 22 Apr 93 20:54:58 GMT
>Message-ID:<m=pv+ka@dixie.com>
>[Offset pins work well and have been pretty standard in racing motorcyle
>engines for over 30 years. The problem with them is there is a strong
>rocking couple at BDC that causes strong slapping. If there is just
>a bit of excess skirt clearance, the slap will break the skirt. voice
>of experience talking. Not much of a problem with high-buck racing
>engines that get new pistons fairly often but a REAL problem with
>econo-motors operated by people with zero budget (me!) I started mounting
>the piston reversed (a la street engines) in order to be able to run
>a season on a piston. A little less power but no more broken skirts.
----I was wondering upon reading this what exactly was meant by reversing the
piston....is it assembling the motor w/ the piston mark (that little dimple on
the piston face) pointing towards the bottom of the motor or what? It always
looked to me that most piston skirts were symetrical...whats the scoop?
[It means installing the piston with the directional arrow pointing
opposite the factory markings. If the piston originally pointed
forward, then the piston is installed pointing to the rear. Piston
skirts typically aren't exactly symetrical. They are designed so the
piston will assume a round cylinder shape at operating temperature and
temperature gradient. What strange cold piston shapes are required are
application- specific but in general, a cold piston tapers toward the
top and is wider across the skirts than across the sides. The thrust
side skirt will sometimes have additional side clearances because that
side gets hotter. But this stuff is not the issue. The issue is where
the wristpin is located. If it is not located on the centerline of the
piston, the pin is offset and the piston will bear a direction marking
of some kind. JGD]